Method for continuously and dynamically mixing at least two fluids, and micromixer

ABSTRACT

The invention relates to a method for continuously and dynamically mixing at least two fluids. Said method comprises the following steps: a) the rotor ( 1 ) of a micromixer is rotatably driven, said micromixer comprising a rotor ( 1 ) which is provided with a shaft ( 2 ) encompassing blades ( 3 ) that are arranged in groups ( 3   a - 3   g ), a stator ( 4 ) which is provided with at least one inlet ( 5 ) for a first fluid, at least one inlet ( 6 ) for a second fluid, and an outlet ( 7 ); b) the fluids are fed into the micromixer; and c) a micromixture of the fluids is collected at the outlet ( 7 ) of the micromixer. The inventive method is particularly suitable for rapid and/or complex kinetic chemical reactions such as anionic polymerization. The invention also relates to a micromixer for carrying out said method.

The present invention relates to a method for continuously anddynamically mixing at least two fluids. This method is particularlysuitable for rapid and/or complex kinetic chemical reactions such asanionic polymerizations.

The invention also relates to a micromixer which is able to implementthis method.

Currently, one of the most commonly used techniques for mixing two ormore liquids consists of using a closed, semi-closed or open vessel,equipped with a mechanical stirrer of propeller, turbine or similartype, and injecting one or more of the reagents into the vessel.

The mixing can be carried out due to the energy dissipated by themechanical stirring. Unfortunately, in certain cases, these devices donot allow micromixing times to be achieved which are sufficiently shortfor rapid and complex reactions to be implemented, and above all, theyare unsuitable in the case of polymerization reactions where theviscosity increases rapidly over time.

The static mixers, placed in line in a conduit or at the inlet of areactor, allow a good mixing of the liquids. Nevertheless, they are,most of the time, used as premixers before entering into a reactor orwhen the constraints of time or viscosity are not redhibitory. Thesedevices are good for homogenizing solutions, but are not really suitablefor certain polymerization reactions, in particular rapid reactions,because the risks of blocking up are significant. This is the case, inparticular, for polymerizations with high levels of solid.

The tangential jet mixers (which can be used in particular for anionicpolymerizations as described in EP-A-0749987) or RIM (“ReactionInjection Molding”) mixing heads are confined jet mixers, i.e. with jetsin contact with the wall of the mixer. They are very efficient, butcause blockages when high polymer contents are involved, or require theinjection of products by pumps which are resistant to high pressures(several hundreds of bars). Moreover the RIM mixing heads requirediscontinuous operation.

The mixer by impact of free jets (i.e. without the jets being in contactwith the walls of the mixer) is known and has been described forcreating emulsions or in liquid-liquid extraction methods, for exampleby Abraham TAMIR, “Impinging-Stream Reactors. Fundamentals andApplications”, Chap. 12: Liquid-Liquid Methods, Elsevier (1994).

Devices with free jet impact have also been described for precipitationor polymerization. They are constituted by two jets orientated accordingto a given angle and the impact of which causes a rapid micromixing; cf.Amarjit J., Mahajan and Donald J. Kirwan “Micromixing Effects in a TwoImpinging-Jets Precipitator, Aiche Journal, Vol. 42, no. 7, pages1801-1814 (July 1996); Tadashi Yamaguchi, Masayuki Nozawa, Narito Ishigaand Akihiko Egastira “A Novel Polymerisation Method by Means ofImpinging Jets”, Die Angewandte Makromolekulare Chemie 85 (1980) 197-199(no. 1311). The drawback of these systems is that they only allow themixing of two fluids and that the jets are all of the same diameter and,consequently, if the mixture is to be effective, the respective flowrates in each jet must be the same. In the case of a polymerizationreaction, the monomer arriving in a first jet and the initiator solutionin a second jet with the same flow rate as the first, it is thus seenthat the quantity of solvent in the system is necessarily relativelylarge, which means that recycling operations, which are generallycostly, have to be envisaged downstream of the polymerization method.

Then a method was developed which is described in the French patentapplication published under the no. 2 770 151 for continuously mixing byfree jet impact at least 2 fluids and recovering the mixture in the formof a resulting jet, so as to overcome the limitations which have justbeen described.

However, the drawback of this system is that it requires a very preciseadjustment of the injection device in order that the jets of fluidscorrectly come into contact at a given point.

In the international patent application published under the no. WO97/10273 a device is described for dispersing isocyanate-terminatedpolyurethane prepolymers comprising a dynamic mixer allowing an averageresidence time of 10 to 120 seconds to be achieved. However, this typeof mixer is not suitable for the more rapid reactions whose averageresidence time in the mixer must be much shorter, in order to allow amixing of the reagents in a sufficiently short time compared to thereaction half-life. As when the reaction and mixing rates are of thesame order of magnitude, strong competition arises between these twomethods. Thus, as this international application shows, a slow reactiondoes not require a very rapid mixing method, while the development of arapid reaction is greatly disturbed by a slow mixing.

The object of the European patent application published under the no. EP824 106 is a method for the preparation of cellulose particles whichhave cationic and/or anionic groups, in which a dynamic mixer is usedcomprising a stator and a rotor equipped with blades of cylindricalshape. The drawback of such a mixer is that the aggregates of matter aresubjected to multiple velocity gradients which stretch and contract themin a random way, causing very significant concentration gradients.

The present invention thus aims to propose a method and a mixer fordynamically and continuously mixing at least two fluids.

It advantageously applies to the mixing of reactive fluids and inparticular, to the anionic polymerization of at least one (meth)acrylicmonomer.

Thus, the subject of the invention is a method comprising the followingsteps:

-   -   a) driving in rotation the rotor of a micromixer comprising:        -   a rotor comprising a shaft equipped with blades distributed            in groups, the blades of each group being arranged around            the shaft in the same plane perpendicular to the            longitudinal axis of the shaft, and the groups of blades            being spaced out from each other along the longitudinal axis            of the shaft;        -   a stator in the form of a hollow cylinder which is able to            receive the rotor, this stator comprising, at one end of its            longitudinal axis, at least one inlet for a first fluid, at            least one inlet for a second fluid and, at the other end of            its longitudinal axis, an outlet for the micromixture of the            fluids;    -   b) introducing the fluids into the micromixer; and    -   c) recovering at the outlet of the micromixer a micromixture of        the fluids.

A subject of the invention is also a micromixer comprising:

-   -   a rotor comprising a shaft equipped with blades distributed in        groups, the blades of each group being arranged around the shaft        in the same plane perpendicular to the longitudinal axis of the        shaft, and the groups of blades being spaced out from each other        along the longitudinal axis of the shaft; and    -   a stator in the form of a hollow cylinder which is able to        receive the rotor, this stator comprising, at one end of its        longitudinal axis, at least one inlet for a first fluid, at        least one inlet for a second fluid and, at the other end of its        longitudinal axis, an outlet for the micromixture of the fluids.

Such a micromixer has the double advantage of not inducing a largepressure loss and being able to be easily adjusted so as to adapt tochanges in the operating conditions such as the flow rates andviscosities. In fact it only requires changing the speed of rotation ofthe rotor, the shape of the blades or counter-blades, or their number.

Moreover, the effectiveness of the mixing does not diminish along thelongitudinal axis of the rotor as is the case in a standard mixer in theshape of a tube.

Moreover, the micromixer according to the invention is very effectiveeven when the viscosities are high.

According to another aspect of the invention, a polymerization method isproposed, in which the method of dynamically and continuously mixing andthe micromixer according to the invention are used.

This method comprises the following steps:

-   -   (i) driving in rotation the rotor of a micromixer comprising:        -   a rotor comprising a shaft equipped with blades distributed            in groups, the blades of each group being arranged around            the shaft in the same plane perpendicular to the            longitudinal axis of the shaft, and the groups of blades            being spaced out from each other along the longitudinal axis            of the shaft;        -   a stator in the form of a hollow cylinder which is able to            receive the rotor, this stator comprising, at one end of its            longitudinal axis, at least one inlet for a first fluid, at            least one inlet for a second fluid and, at the other end of            its longitudinal axis, an outlet for the micromixture of the            fluids;    -   (ii) introduction of at least two fluids, at least one of which        is reactive, into the micromixer;    -   (iii) recovery at the outlet of the micromixer of a micromixture        of the fluids;    -   (iv) polymerization of the reactive fluid or fluids, this        polymerization being able to occur outside the micromixer or        begin inside this micromixer and continue outside this        micromixer.

Other characteristics and advantages of the invention will now bedescribed in detail in the following description which refers to thefigures, in which:

FIG. 1 represents schematically and in an exploded front view, amicromixer according to the invention;

FIG. 2 represents schematically and in a top view, a rotor of themicromixer of FIG. 1;

FIG. 3 represents schematically and in a top view, a disk of the statorof the micromixer of FIG. 1;

FIG. 4 represents schematically and in a top view, the assembly of thedisk of FIG. 3 and of the rotor of FIG. 2;

FIG. 5 represents schematically and in partial section, a micromixeraccording to the invention;

FIGS. 6 and 7 are curves showing the influence of the speed of rotationof the rotor of the micromixer according to the invention, on thequality of product obtained, at constant flow rates;

FIGS. 8 and 9 are curves showing the influence of the flow rates of thefluids on the quality of product obtained, at a constant speed ofrotation of the rotor of the micromixer according to the invention;

FIGS. 10 and 11 are curves showing the influence of the type of mixerused on the quality of product obtained, at constant flow rates.

DETAILED DESCRIPTION OF THE INVENTION

Mixing Method According to the Invention

The method for dynamically and continuously mixing according to theinvention has been described in a general way above.

It can be implemented for mixing more than two fluids. However, for thesake of simplicity, it will now be described for an implementation withtwo fluids.

According to the invention, the rotor can be driven in rotation at aspeed which can reach up to 30,000 r.p.m.

Preferably, a speed of rotation of the rotor greater than 5,000 r.p.m ischosen, in order to obtain a homogeneous mixing and less than 20,000r.p.m, so as to limit overheating phenomena.

The introduction of the first and second fluids preferably occurs in atleast two places which are diametrically opposed with respect to theaxis of the rotor of the micromixer.

The method according to the invention is generally used with a fluidtemperature comprised between −100° C. and 300° C. It is preferably usedwith temperatures comprised between −80° C. and 110° C.

It can be implemented with fluid pressures comprised between 0.1 and 100bars absolute. Preferably, it is used with pressures comprised between 1and 50 bars absolute.

The fluids can be introduced into the mixer at a flow rate between 1 g/hand 10,000 kg/h. Preferably, the flow rate of the fluids is comprisedbetween 1 kg/h and 5,000 kg/h.

The ratio of the mass flow rates of the fluids can be very variable. Itis generally comprised between 0.01 and 100, preferably between 0.1 and10.

The method according to the invention can allow mixing of fluids whoseviscosity is comprised between 1 mpa.s and 10³ Pa.s. Preferably, thisviscosity is comprised between 10 mPa.s and 10 Pa.s.

The method according to the invention is used with residence times forthe fluids in the micromixer generally greater than 1 ms. Preferably,the operating conditions are adjusted so that the residence time iscomprised between 5 ms and 10 s.

Polymerization Method According to the Invention

The mixing method which has just been described is particularly suitablefor the micromixing of reactive fluids. It preferably applies toreactive liquids.

It can thus advantageously be implemented for the production of anintimate mixture of liquids which is to produce chemical reactions withrapid and/or complex kinetics, such as anionic polymerizations, orpolymerizations with high levels of solid.

Thus, the mixing method according to the invention can constitute a partof a more global polymerization method.

This polymerization method according to the invention in particularapplies to the mixture of reactive fluids intended for anionicpolymerization, at least one of which comprises at least one(meth)acrylic monomer.

As (meth)acrylic monomer, there can thus be mentioned in particularacrylic anhydride, methacrylic anhydride, methyl, ethyl, propyl, n- andtert-butyl acrylates, ethylhexyl, nonyl, 2-dimethyl amino ethyl andmethyl, ethyl, propyl and n- and tert-butyl methacrylates, ethylhexyl,nonyl and 2-dimethyl amino ethyl.

The actual polymerization can occur outside the micromixer according tothe invention, or it can begin inside the micromixer and continueoutside this micromixer, for example in an appropriate reactor.

The method according to the invention can be used in any polymerizationinstallation. In particular the one illustrated by FIG. 1 on page 14 ofthe aforementioned patent application EP 749 987 can be mentioned.

The method according to the invention can in particular be used for thepreparation of polymers according to the methods described in Europeanpatent applications published under the numbers EP 749 987, EP 722 958and EP 524 054.

Micromixer According to the Invention

The micromixer according to the invention is able to implement themethod which has just been described.

This micromixer has been described in a general way above.

For more details about its structure reference can be made to FIGS. 1 to6 which give an illustration of the structure of this micromixer.

In FIG. 1 in particular, it is seen that the micromixer according to theinvention comprises a rotor 1 comprising a shaft 2 of approximatelycylindrical shape equipped with blades 3.

These blades 3 are distributed in groups 3 a, 3 b, 3 c, 3 d, 3 e, 3 fand 3 g, the blades of each group are arranged around the shaft 2, inthe same plane perpendicular to the longitudinal axis of the shaft 2,and the groups of blades being spaced out from each other along thelongitudinal axis of the shaft 2. This can be seen clearly in FIG. 1,where each group 3 a to 3 g has the appearance of a disk.

In FIG. 2, a top view of the rotor is shown. Thus a group 3 a of sixblades 3 is seen. The blades are arranged regularly around the shaft, ina star and each is inclined at 60 degrees with respect to its twonearest neighbours.

The blades are approximately identical to each other and are in the formof a cutting edge. One of their longitudinal sides forms a tangent atthe circumference of the shaft 2. The free end of each blade 3 can betapered.

A 60 degree rotation of the shaft allows one blade to occupy the placethat one of its two neighbours occupied before this rotation.

The blades 3 of a group of blades 3 a are preferably alignedrespectively with the blades of another group of blades 3 b along thelongitudinal axis of the rotor, so that in a top view and looking in thedirection of the longitudinal axis of the rotor 1 (FIG. 2), only onegroup of blades can be seen, the others being hidden beneath them.

The rotor 1 is intended to cooperate with a stator 4 which is seenfirstly in FIG. 1. This stator 4 has approximately the form of a hollowcylinder. It has dimensions which make it able to house at least partlythe rotor 1.

As is seen in FIG. 5, the stator 4 comprises at one end of itslongitudinal axis, an inlet 5 for a first fluid, an inlet 6 for a secondfluid and at the other end of its longitudinal axis, an outlet 7 for themicromixture of fluids.

Preferably, the inlet 6 is diametrically opposed with respect to theinlet 5.

According to one embodiment of the invention, the stator 4 comprisesdisks 8 which are seen out of the stator in FIG. 1.

When the stator 4 is mounted, as is seen in FIG. 5, the disks 8 arestacked inside.

The specific shape of the disks 8 can be seen in FIG. 3. Each disk 8 hasin its centre a recess 9 which allows it to house a group of blades 3 aor 3 b to 3 g, while allowing the latter to turn together with the rotor1.

The recess 9 has the shape of a circular hole, one part of which isoccupied by extensions 10 of the disk 8. These extensions 10 projectwith respect to the wall 11 of the disk 8 delimiting the recess 9.

These extensions 10 of the disks 8 have approximately the same shape andthe same dimensions as the blades 3 of the rotor 1. That is why in theremainder of the present description they are called counter-blades 10.

Each disk 8 thus comprises its group of six counter-blades 10 arrangedin a regular manner on the circumference of the wall 11. Eachcounter-blade is inclined at 60 degrees with respect to its two nearestneighbours.

As for the blades 3 of the rotor 1, a 60 degree rotation of a disk 8allows a counter-blade 10 to occupy the place that one of its twoneighbours occupied before this rotation.

The counter-blades 10 of a group of counter-blades 10 are alsopreferably aligned respectively with the counter-blades of another groupof counter-blades 10 along the longitudinal axis of the stator, so thatin a top view and looking in the direction of the longitudinal axis ofthe stator 4 (FIG. 3), only one group of counter-blades 10 can be seen,the others being hidden beneath them.

FIG. 4 shows, in a top view, a group of blades 3 of the rotor 1 aroundwhich a disk 8 has been placed.

With reference to FIG. 5, it is noted that the counter-blades 10 have athickness less than that of the body 12 of the disk 8 which they extend.

The disks 8 are in contact with each other, stacked inside the stator 4,so that each group of blades 3 (with the exception of the first and thelast) is inserted between two groups of counter-blades 10.

Thus, when the shaft 2 of the rotor 1 turns, each group of blades 3 canturn freely, i.e. without being impeded by the adjacent groups ofcounter-blades 10. The blades 3 and the counter-blades 10 are preferablyinclined in opposite directions so that, during rotation of the rotor,they come close to each other like the blades of shears, and thus causeshearing of the fluids.

Moreover, looking from the inlet 5 of the micromixer towards its outlet7, it is noted that a space 13 is provided, in longitudinal direction,between each group of blades 3 and the group of counter-blades 10 whichprecedes it (except in the case of the first group of blades situatedclose to the inlet of the stator) and another space 14 is also providedbetween each group of blades 3 and the group of counter-blades 10 whichfollows it (except in the case of the last group of blades situatedclose to the outlet of the stator).

Moreover, as is seen in FIG. 4, when the rotor/stator assembly is seenin cross section, it is noted that the sum of the surface areas of theshaft 2, the blades 3 and the counter-blades 10 is less than the surfacearea of the circular hole delimited by the wall 11 of the disk 8, sothat there are still spaces 15 allowing the circulation in thelongitudinal direction of the fluids being mixed.

The spaces 15 have a minimum size in the case of FIG. 4, where the sideof each blade 3 which is tangential to the shaft 2 is arranged parallelto the longitudinal sides of a counter-blade 10.

The spaces 15 have a maximum size when, looking in the direction of theaxis of the shaft 2, the blades 3 are superposed on the counter-blades10 and hide them.

As can be deduced from FIG. 5, a bore 16 can be provided through thethicknesses of the disks 8 and in the stator 4, in order to be able tointroduce a rod or a screw (not represented) in order to immobilize thedisks 8 and make them integral with the stator 4.

Generally, the stator 4 also comprises a fluid distributor 17approximately in the form of a washer and situated at the level of thefeed of the stator 4 and upstream of the disks 8, if referring to thegeneral direction of circulation of the fluids.

One end of the distributor 17 is in annular contact with the first disk8.

The distributor 17 comprises at least one opening for the first fluidand at least one other opening for the second fluid, these openingsbeing cut in the washer radially and communicating respectively with theentries 5 and 6 of the stator 4.

Thus, the fluids entering through the entries 5 and 6 are taken throughthe openings of the distributor 17 close to the shaft 2 of the rotor 1.

Generally, the central hole 18 of the distributor 17 has a diameterapproximately the same as that of the circular hole of a disk 18delimited by the wall 11 of this disk. It follows that when the rotor 1is mounted in the stator 4, a first group of blades 3 of the rotor 1 canoptionally be inserted inside the central hole 18 and turn freelytherein.

At its lower end, i.e. the one opposite the one which is in contact witha disk 18, the distributor 17 optionally has a bore 19 intended toreceive a ring seal 20 which is also in contact with the shaft 2 of therotor 1.

The stator 4 is generally-fixed onto a support 21 in a standard wayusing a bolt (not represented).

Operation of the Micromixer

The rotor 1 is generally driven in rotation in a standard way by meansfor driving in rotation such as an electric motor (not represented).However, a motor capable of maintaining a constant speed of rotation,independent of the resisting torque to which it can be subjected, (e.g.milling machine motor), is preferably chosen.

The direction of rotation of the rotor is that of the inclination of theblades 3.

As is seen by observing FIG. 5, the micromixer is fed through the inlet5 using a first fluid and through the inlet 6 using a second fluid.

The openings of the distributor 17 take the fluids towards the centre,into the central hole 18. The fluids are then confined between the shaft2 and the walls of the central hole 18 and are in contact with a firstgroup of blades 3.

Under the effect of the pressure of the fluids and of the rotation ofthe shaft 2, the first blades, in cooperation with the firstcounter-blades, shear the fluids which progress through the spaces 14,then 15 and 13.

The fluids then rapidly encounter other blades 3 and counter-blades 10until outlet 7 of the mixer where they are intimately mixed.

The intimate mixture of the fluids can then be used in numerousapplications.

For example, it can be introduced into a tubular reactor or similar, andchemical reactions can occur, as described previously.

EXAMPLES

The following examples illustrate the present invention without howeverlimiting its scope.

In these examples, the polymerization installation used is the onerepresented schematically in FIG. 1, page 14 of the aforementionedEuropean patent application no. EP 749 987 and in which, as mixer M, amicromixer according to the invention is used having the followingcharacteristics:

-   -   internal volume of the micromixer: 1.62 ml    -   diameter of the rotor shaft in the mixing zone: 5.4 mm    -   thickness of the blades of the rotor: 1 mm    -   thickness of the counter-blades of the disks: 1 mm    -   space, measured in the direction of the longitudinal axis of the        rotor, between a counter-blade of the rotor and each of the        adjacent rotor blades: 0.4 mm (thickness of the disks of the        stator: 2.8 mm)    -   number of groups of blades: 7    -   number of disks: 6

The triblocks (triblock copolymers) ABC 100, ABC 101 and ABC 104 asidentified in Examples 1 to 6 are prepared according to the operatingmethod described in the European patent application published under thenumber EP 524 054 or in the aforementioned application EP 749 987.

The following abbreviations were used:

-   PS: polystyrene-   BP: polybutadiene-   PMMA: poly(methylmethacrylate)-   SB: diblock(diblock copolymer)poly(styrene-b-butadiene)-   SBM: triblock (triblock terpolymer formed by a polystyrene block, a    polybutadiene block and a poly(methyl methacrylate) block-   ABC 100: PS-b-PB-b-PMMA (terpolymer formed by a polystyrene block, a    polybutadiene block and a poly(methyl methacrylate) block, with a    mass composition (32/35/33) and having an average molecular mass by    numbers of the polystyrene block, M_(n) (PS), of 27,000 g/mol-   ABC 101: PS-b-PB-b-PMMA with a mass composition (20/30/50) and    having an average molecular mass by numbers Mn (PS) of 20,000 g/mol-   ABC 104: PS-b-PB-b-PMMA with a mass composition (20/30/50) and    having an average molecular mass by numbers M_(n) (PS) of 20,000    g/mol-   Q(SB): flow rate in kg/h of the poly(styrene-b-butadiene)-butadienyl    lithium solution, at the inlet of the micromixer,-   Q(M): flow rate of the methyl methacrylate solution at the inlet of    the micromixer in kg/h-   V0: 0 r.p.m.-   V1: approximately 7,600 r.p.m.-   V2: approximately 11,200 r.p.m.-   V3: approximately 15,000 r.p.m.-   V4: approximately 18,500 r.p.m.-   114T: example according to the prior art, in which the standard    tangential jet mixer as described in EP 749 987 is used-   Ve: elution volume

The average molecular mass in numbers of the PS block was determined bysteric exclusion chromatography (SEC) in polystyrene equivalent, aftersampling this block during the experiment.

The mass fractions of PS, PB and PMMA were determined by proton NMR.

The products contain a homopolystyrene (PS) fraction and a diblockcopolymer fraction poly(styrene-b-butadiene) (SB), these fractionsresulting from a non-quantitative blocking efficiency under thesynthesis conditions used.

In all cases, the glass transition temperature (Tg) of the PB block isapproximately −90° C.

The PMMA blocks are syndiotactic at more than 70% and have a T_(g) of135° C.

In Examples no. 1 to 6, the results of SEC are superposed in order forthe tests carried out to be better visualized.

Example 1

The influence of the speed of rotation of the rotor of the micromixeraccording to the invention on the quality of an synthesized ABC 100triblock is studied.

For this purpose, at one inlet of the micromixer, a solution ofpoly(styrene-b-butadiene)-butadienyl lithium and at the diametricallyopposed inlet of the micromixer, a solution of methyl methacrylate isintroduced.

The flow rates are kept constant, namely, 40 kg/h for Q(SB) and 20 kg/hfor Q(M).

After polymerization in the tubular reactor, measurement by SEC iscarried out of the intensity of the I(RD) detection as a function of theelution volume Ve.

The results are shown in the form of curves in FIG. 6, each curvecorresponding to a speed of rotation of the rotor.

No notable difference is observed between the synthesized ABC 100 whenpassing from V1 to V4.

In all cases, the presence of residual SB in the product obtained isnoted.

But the proportion of SB in the synthesized ABC 100 is significantlyhigher at V0 than for V1, V2, V3, or V4.

This can be explained by the fact that when chemical reactions are inplay, it is the bringing into contact of the reagents, the mixing on themolecular level which is important. However, the polmerization kineticsof methacrylates under these conditions is extremely rapid. Moreover, itis known that the efficiency of mixing required for a reactor depends onthe relationship between the characteristic time of the reactionconsidered and the mixing time on the molecular level.

In the case of mixing at V0, the volume energy dissipated in themicromixing zone is smaller, which results in the contact between thereagents being less intimate.

A heterogeneous distribution of the reagents results which causesunwanted reaction terminations.

In other words, the peaks are narrower for V1 to V4, which shows thatthe dynamic micromixer according to the invention is more effective at aspeed greater than V0.

Example 2

The influence of the speed of rotation of the rotor of the micromixeraccording to the invention on the quality of a synthesized ABC 101triblock is studied.

For this purpose, the operation is carried out as in Example 1.

The results are shown in FIG. 7.

The same conclusions as in Example 1 are reached, namely:

-   -   no notable difference is observed between the synthesized ABC        101 when passing from V1 to V4.;    -   in all cases, the presence of residual SB in the product        obtained is noted;    -   the proportion of SB in the synthesized ABC 100 is significantly        higher at V0 (static mixer) than for V1, V2, V3, or V4, which        again shows that the dynamic micromixer according to the        invention performs better than a static mixer.

Example 3

In this example, in a micromixer according to the invention, theinfluence of the total flow rate Q (SB)+Q(M), with a constant flow rateratio Q(SB)/Q(M) and a constant speed of rotation of the rotor, on thequality of a synthesized ABC 100 triblock is studied.

In a first case, the sum of the flow rates Q(SB) and Q(M), respectively,30 kg/h and 15 kg/h, is equal to 45 kg/h.

In a second case, the sum of the flow rates Q(SB) and Q(M),respectively, 40 kg/h and 20 kg/h, is equal to 60 kg/h.

The results are shown in FIG. 8.

It is noted that the increase in the total flow rate leads to betterresults.

Example 4

The same study as in Example 3 is undertaken, but synthesizing an ABC101 triblock instead of the previous ABC 100 triblock.

The results are shown in FIG. 9.

It is noted that for this product, ABC 101, the variation in the totalflow rate has very little influence on the quality of the synthesizedproduct, from the time when this flow rate has reached a minimum valuewhich is sufficient to allow a characteristic micromixing time which isshorter than the reaction time.

Example 5

In this example, the results obtained with three types of mixers werecompared, namely:

-   -   a tangential jet mixer (114T);    -   a static mixer (speed V0); and    -   the mixer according to the invention (speed V2).

In the three cases, ABC 104 was synthesized with constant flow rates,Q(SB)=30 kg/h and Q(M)=15 kg/h.

The results are shown in FIG. 10.

The following is noted:

-   -   on the one hand, a significant improvement in the rate of        coupling (which results in a fall in the quantity of residual SB        diblock in the SBM), when using a tangential jet or dynamic        mixer rather than a static mixer, and    -   on the other hand, a notable improvement in the quality of the        coupling when passing from a tangential jet mixer to the mixer        according to the invention.

These results are expressed by different dispersities of population ofthe different chains, i.e. by different polymolecularity indexes (Ip):

-   -   Ip=2.45 for the static mixer;    -   Ip=2.01 for the tangential jet mixer;    -   Ip=1.80 for the dynamic mixer according to the invention.

Example 6

In this example, the operation is carried out as in Example 5, exceptthat higher total flow rates were used, namely, 60 kg/h instead of 45kg/h.

The results are shown in FIG. 11.

The same conclusions are reached as in Example 5.

A significant improvement in the Ip is also noted in the case of thestatic mixer. Specifically:

-   -   Ip=2.02 for the static mixer;    -   Ip=1.98 for the tangential jet mixer;    -   Ip=1.80 for the dynamic mixer according to the invention.

Nevertheless, the dynamic mixer according to the invention is clearlyperforms better than the tangential jet mixer and a fortiori than thestatic mixer.

1. Method for continuously and dynamically mixing at least two fluids,comprising the following steps: a) driving in rotation the rotor (1) ofa micromixer comprising: a rotor (1) comprising a shaft (2) equippedwith blades (3) distributed in groups (3 a-3 g), the blades (3) of eachgroup (3 a-3 g) being arranged around the shaft (2) in the same planeperpendicular to the longitudinal axis of the shaft (2), and the groups(3 a-3 g) of blades (3) being spaced out from each other along thelongitudinal axis of the shaft (2); a stator (4) in the form of a hollowcylinder which is able to receive the rotor (1), this stator (4)comprising, at one end of its longitudinal axis, at least one inlet (5)for a first fluid, at least one inlet (6) for a second fluid and, at theother end of its longitudinal axis, an outlet (7) for the micromixtureof the fluids; b) introducing the fluids into the micromixer; and c)recovering at the outlet (7) of the micromixer a micromixture of thefluids.
 2. Method according to claim 1, characterized in that the rotor(1) is driven in rotation at a speed equal to 30,000 r.p.m. at most andpreferably greater than 5000 r.p.m. and less than 20,000 r.p.m. 3.Method according to claim 1, characterized in that the first and secondfluids are introduced in at least two places (5, 6) diametricallyopposed with respect to the axis of the rotor (1).
 4. Method accordingto claim 1, characterized in that it is used with a fluid temperaturecomprised between −100° C. and 300° C. and preferably comprised between−80° C. and 110° C.
 5. Method according to claim 1, characterized inthat it is implemented with fluid pressures comprised between 0.1 and100 bars absolute and preferably comprised between 1 and 50 barsabsolute.
 6. Method according to claim 1, characterized in that thefluids are introduced into the mixer at a flow rate between 1 g/h and10,000 kg/h and preferably between 1 kg/h and 5,000 kg/h.
 7. Methodaccording to claim 1, characterized in that the ratio of the mass flowrates is comprised between 0.01 and 100, preferably between 0.1 and 10.8. Method according to claim 1, characterized in that the fluids have aviscosity comprised between 1 mPa.s and 10³ Pa.s and preferablycomprised between 10 mPa.s and 10 Pa.s.
 9. Method according to claim 1,characterized in that it is implemented with residence times of thefluids in the micromixer greater than 1 ms, and preferably, comprisedbetween 5 ms and 10 s.
 10. Method according to claim 1, characterized inthat the fluids are reactive fluids.
 11. Method according to claim 10,characterized in that the fluids are liquids which produce anionicpolymerization reactions.
 12. Method according to claim 11,characterized in that at least one of the fluids comprises at least one(meth)acrylic monomer.
 13. Method according to claim 12, characterizedin that the (meth)acrylic monomer is chosen from the group constitutedby acrylic anhydride, methacrylic anhydride, acrylates of methyl, ethyl,propyl, n- and tert-butyl, ethylhexyl, nonyl, 2-dimethyl amino ethyl andmethacrylates of methyl, ethyl, propyl and n- and tert-butyl,ethylhexyl, nonyl and 2-dimethyl amino ethyl.
 14. Polymerization method,comprising the following steps: (i) driving in rotation the rotor (1) ofa micromixer comprising: a rotor (1) comprising a shaft (2) equippedwith blades (3) distributed in groups (3 a-3 g), the blades (3) of eachgroup (3 a-3 g) being arranged around the shaft (2) in the same planeperpendicular to the longitudinal axis of the shaft (2), and the groups(3 a-3 g) of blades (3) being spaced out from each other along thelongitudinal axis of the shaft (2); a stator (4) in the form of a hollowcylinder which is able to receive the rotor (1), this stator (4)comprising, at one end of its longitudinal axis, at least one inlet (5)for a first fluid, at least one inlet (6) for a second fluid and, at theother end of its longitudinal axis, an outlet (7) for the micromixtureof the fluids; (ii) introduction of at least two fluids, at least one ofwhich is reactive, into the micromixer; (iii) recovery at the outlet (7)of the micromixer of a micromixture of the fluids; (iv) polymerizationof the reactive fluid or fluids, this polymerization being able to occuroutside the micromixer or begin inside this micromixer and continueoutside this micromixer.
 15. Polymerization method according to claim14, in which at least one of the fluids comprises at least one(meth)acrylic monomer.
 16. Polymerization method according to claim 15,characterized in that the (meth)acrylic monomer is chosen from the groupconstituted by acrylic anhydride, methacrylic anhydride, acrylates ofmethyl, ethyl, propyl, n- and tert-butyl, ethylhexyl, nonyl, 2-dimethylamino ethyl and methacrylates of methyl, ethyl, propyl and n- andtert-butyl, ethylhexyl, nonyl and 2-dimethyl amino ethyl.
 17. Micromixercomprising: a rotor (1) comprising a shaft (2) equipped with blades (3)distributed in groups (3 a-3 g), the blades (3) of each group (3 a-3 g)being arranged around the shaft (2) in the same plane perpendicular tothe longitudinal axis of the shaft (2), and the groups (3 a-3 g) ofblades (3) being spaced out from each other along the longitudinal axisof the shaft (2); and a stator (4) approximately in the form of a hollowcylinder which is able to receive the rotor (1), this stator (4)comprising, at one end of its longitudinal axis, at least one inlet (5)for a first fluid, at least one inlet (6) for a second fluid and, at theother end of its longitudinal axis, an outlet (7) for the micromixtureof the fluids;
 18. Micromixer according to claim 17, characterized inthat the stator (4) also comprises a plurality of disks (8), these disks(8) being stacked and arranged inside the stator (4), each disk havingin its centre a recess (9) housing a group (3 a-3 g) of blades (3). 19.Micromixer according to claim 18, characterized in that the recess (9)of each disk (8) has the shape of a circular hole, one part of which isoccupied by extensions of the disk (8) forming counter-blades (10). 20.Micromixer according to claim 19, characterized in that thecounter-blades (10) of the disks (8) have the same shape and the samedimensions as the blades (3) of the rotor (1) and have a thickness lessthan that of the body (12) of the disk (8).
 21. Micromixer according toclaim 17, characterized in that the inlets (5, 6) of the stator arediametrically opposed.
 22. Micromixer according to claim 17,characterized in that it also comprises a fluid distributor 17 in theform of a washer, this distributor (17) comprising at least one inletfor a first fluid and at least one inlet for a second fluid, theseinlets communicating respectively with the inlets (5, 6) of the stator(4).